1. Field of the Invention
The present invention relates to a print color predicting method, a print color predicting apparatus, a computer-readable recording medium with a print color predicting program recorded therein, and a profile generating method, which are capable of predicting color reproduction of a protective-film-covered print, in which a printed object is covered by a protective film.
2. Description of the Related Art
With significant advances in inkjet technology in recent years, it has been become possible for inkjet printers to produce large color prints of high quality at high speeds. Inkjet printers are not only popular for private or home use, but also are widely used in commercial applications nowadays. Inkjet printers enable prints to be made on POP (Point Of Purchase) posters, wall posters, large-size mediums such as outdoor advertisements and billboards, roll mediums, and thick hard mediums.
There are a wide variety of print mediums (hereinafter also referred to as “mediums”) available for use in prints in order to meet various commercial demands. For example, such print mediums include paper mediums including synthetic paper, thick paper, aluminum-evaporated paper, etc., resin mediums made of vinyl chloride, PET, etc., and tarpaulin paper made of a woven fiber cloth with synthetic resin films applied to both surfaces thereof.
Since advertisement prints are expected to be effective in arousing consumers' motivation to buy advertised products through visual sensation, the finish of colors of the prints (printed mediums) is of particular importance. Heretofore, there have been disclosed various color matching technologies, such as a method of generating an ICC (International Color Consortium) profile, a method of adjusting a designated color, etc., as print color managing process.
Advertisement prints are displayed in a variety of places including outdoor areas, indoor areas, and spotlighted exhibition sites. Generally, the spectral characteristics (spectral energy distribution) of environmental light as an observational light source for prints vary depending on different places where the prints are displayed. As a result, in cases where the observational light sources differ, even though the same print is viewed, the spectral characteristics of light that ultimately reaches the retinal wall of eyes of the observer are different, and therefore, the appearance of the print (impression of colors) to the observer is subject to variation, although the tendency may differ from observer to observer. As a consequence, if the observational environment in which a print is produced (i.e., the location where the printer is installed) and the observational environment in which the print is displayed differ greatly from each other, then the print may possibly fail to exhibit desired colors.
As one method for solving such problems, Japanese Laid-Open Patent Publication No. 2007-081586 discloses a method and apparatus for storing independently spectral data of a print, and a plurality of light source spectral data. A profile appropriate for an observational light source is generated each time that the observational light source is set up. This publication states that the method and apparatus can generate profiles corresponding to respective different observational light sources for colorimetric measurement in a reduced number of man-hours, and can perform appropriate color management for prints depending on such observational light sources.
Prints produced by inkjet printers may not endure in severe environments because the images thereof are not highly durable, particularly in terms of abrasion resistance and toughness.
For example, in exhibition sites that are exposed to high intensity radiant light at all times, color images of displayed prints tend to become gradually discolored because the dyes included in the inks are gradually decomposed by chemical reactions. Also, in display modes where prints are applied to indoor floors, color images of the prints are likely to become damaged because the print surfaces become abraded by people walking on the floors.
Attempts have been made to increase the durability of print images in such applications by covering the image-formed surfaces of prints with protective films such as laminating films, which are functionally treated by the addition of an ultraviolet absorbent, or through an embossing process.
For example, Japanese Laid-Open Patent Publication No. 06-246881 discloses a protective-film-covered print in which an image-formed surface of print is covered with a protective film. With this feature, the publication states that the quality of a printed surface can be improved in terms of anti-scratch performance and alcohol resistance, as well as anti-permeability.
However, the results of investigation and research conducted by the inventor of the present invention have indicated that, although the laminating film has high transmittance, the spectral transmittance thereof is not necessarily flat within a visible wavelength range, and hence the appearance of printed color images that are covered with the laminating film tends to vary to a non-negligible extent, depending on whether the print is covered with a laminating film or not It also has been discovered that there are many types of commercially available laminating films, which exhibit different spectral transmittances.
Even if the method and the apparatus disclosed in Japanese Laid-Open Patent Publication No. 2007-081586 are applied to the protective-film-covered print disclosed in Japanese Laid-Open Patent Publication No. 06-246881, various prints having various laminating films covering image-formed surfaces thereof (i.e., various protective-film-covered prints) have to be measured colorimetrically, in order to obtain a profile of a protective-film-covered print. However, if colors are to be strictly reproduced with respect to all combinations of laminating films and prints, then it becomes highly tedious and time-consuming to prepare such samples and to colorimetrically measure them. Further, if characteristics of the laminating films are ignored, then the appearance of printed color images through the laminating films varies, depending on the type of laminating film that is used.